import os
import sys

n = int(input())
a = []
for i in range(65, 65 + 26):
    a.append(chr(i))
ans = []
while n > 0:
    n -= 1
    i = n % 26
    n = n // 26
    ans.append(a[i])
ans.reverse()
for an in ans:
    print(an, end="")
